textproduct: Albany

SYNOPSIS

Cold temperatures continue through tonight ahead of a weak clipper for tomorrow evening that will bring light snow to areas mainly near and north of I-90. Then, a stronger disturbance on Wednesday ushers in a period of widespread snow in the morning before it mixes with rain in valley areas followed by upslope and lake effect snow showers Wednesday night into Thursday. The highest accumulations and most impacts are expected in the southern Adirondacks.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Key Messages:

- Winter Storm Watch issued for the southern Adirondacks from 4AM Wednesday through 7AM Thursday where there is a 50 to 80% chance of greater than 6 inches of snow. The highest accumulations will likely remain north of the New York Thruway.

- Winter Weather Advisories will likely be needed in the southern Greens and Upper Hudson Valley on Wednesday where is there a 40 to 80% chance for greater than 4 inches of snow.

Discussion:

Chilly temperatures will continue through tonight across eastern NY and western New England as a broad area of Canadian high pressure centered in the Great Lakes builds eastward. West to northwest winds continue to advect a continental polar (Cp) air mass into the Northeast as latest visible satellite imagery shows widespread snow covering stretching across Central and Eastern Canada into the Great Lakes. With ideal radiational cooling conditions expected tonight including clear skies and light winds under a deep snow pack, very cold overnight lows are likely. In fact, probabilistic guidance from the NBM shows 50 to 75% chances widespread throughout the region for tomorrow morning lows in the single digits with even 40 to 50% chances for below zero readings in the southern Adirondacks and southern Greens. After a very chilly start to our Tuesday, clear skies fade behind increasing clouds Tuesday afternoon ahead of our next weak clipper. However, the associated shortwave incoming from the Great Lakes flattens out and becomes sheared out as it tracks up the Saint Lawrence River Valley tomorrow evening. While overall forcing and moisture look weak, a period of isentropic lift arrives 21 UTC Tues - 00 UTC Wed and spreads from southwest to northeast Tuesday night with guidance suggesting some snow showers break out, especially in the southern Adirondack and southern Greens where upslope looks to enhance precipitation potential. However, even this will have to overcome a dry air mass as PWATs likely remain under 0.50" so only expecting coating up to 2 inches of snow mainly near/north of I-90. The highest amounts likely in the south/southwest facing slopes of the southern Adirondacks and southern Greens.

While we should see a brief break from the snow Tuesday night but the respite will last a few hours as the next system arrives right on its tail. A compact shortwave with Pacific origins will dive into the Upper Midwest before a closed low positioned in the Hudson Valley steers it northward up the Saint Lawrence River Valley tomorrow. As the two begin to phase Wed morning, the shortwave intensifies resulting in increasing forcing for ascent. This includes a strong push of isentropic lift as southerly winds in the 925-850hPa layer increases to 45-50kts which will help direct a plume of moisture from the Gulf northward. Thus, there is increasing confidence that as snow arrives from southwest to northeast Wednesday morning, it will fall moderately to heavily with the HREF showing a 20 to 30% chance for greater than 1 inch per hour snowfall rates in the southern Adirondacks due to upsloping enhancement. Latest guidance shows the snow beginning initially west of the Hudson River 12 - 15 UTC or during the A.M commute before snow quickly spreads eastward. Despite strong southerly winds in the low and mid-levels, expecting a steady period of all snow throughout the region Wednesday morning as wet-bulbing cooling processes likely supports cold enough thermal profiles before enough warming occurs in valley areas by 18 - 21 UTC that snow turns wetter and struggles to accumulate. In addition, isentropic lift by Wed P.M turns weaker as winds shift to the west and a dry slot punches northward leading to lighter precipitation. This also means travel conditions should improve by the Wed P.M commute outside the higher terrain areas. Overall, expecting coating up to 2 inches in the Hudson Valley from the Greater Capital Region southward into the mid-Hudson Valley and NW CT while there is 30 to 70% chance for greater than 7" in the southern Adirondacks (especially along south facing slopes) with only a 30 to 40% chance of 7"+ in the southern Greens. Winter Storm Watches have been issued for all of Herkimer, Hamilton and northern Fulton where probabilities for greater than 7" of snow are highest (mainly north of the NY Thruway). Winter Weather Advisories will likely be need in the southern Greens and in parts of the Upper Hudson Valley but there is low confidence in exceeding 7".

LONG TERM /THURSDAY THROUGH MONDAY/

Key Message:

- Below normal temperatures remain in place along with continued chances of snow showers.

Discussion:

While the strongest moisture transport/forcing exit to our east by 21 - 00 UTC Wed, the main cold front pushes through the region overnight Wednesday. Once the winds shift to the west in the wake of the boundary, winds turn gusty and ensuing cold air advection will support additional snow showers through Thursday morning, mainly in the higher terrain areas. Thursday remains blustery and chilly as the parent closed low swings through Quebec. This will support westerly winds in the low and mid- levels across the Northeast, leading to lake effect snow bands and even a multi-lake connection by Thursday afternoon as a favorable fetch and cold air advection develop over the Great Lakes. We increased POPs to chance Thursday afternoon to help message returning snow showers and additional light snow accumulations, especially in the Mohawk Valley. We remain chilly heading in Thursday night as westerly winds maintain cold air advection.

West to northwesterly flow aloft will continue Friday through next weekend. This will bring continued below normal temperatures to the region. There are some timing differences amongst the members on any additional passing shortwaves, though at least one additional clipper system could bring another round of snow sometime over the weekend. Surface high pressure and rising heights should then bring drier weather by the start of next week.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

Through 00z Wednesday...Flying conditions are currently VFR, and should remain VFR at all terminals through at least the end of the TAF period. SCT to BKN mid and high clouds tonight become BKN to OVC tomorrow, with some mid-level clouds also possible tomorrow afternoon ahead of our next weather system. While it should remain dry through 00z Wednesday, some snow showers are possible shortly after this. Winds will generally be calm tonight through mid to late morning tomorrow, then increase to 5-10 kt from the S/SE. Gusts of up to around 15kt will be possible tomorrow late afternoon and evening at ALB/PSF.

Outlook...

Tuesday Night: Low Operational Impact. Slight Chance of SN. Wednesday: High Operational Impact. Definite SN. Wednesday Night: High Operational Impact. Likely SHSN. Thursday: Moderate Operational Impact. Breezy. Chance of SHSN. Thursday Night: Low Operational Impact. Slight Chance of SHSN. Friday: Low Operational Impact. Slight Chance of SHSN. Friday Night: Moderate Operational Impact. Chance of SN. Saturday: Moderate Operational Impact. Chance of SN.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...Winter Storm Watch from late Tuesday night through Thursday morning for NYZ032-033-038-082. MA...None. VT...None.